CALGARY -- Athabasca Oil (TSX:ATH) has resumed operations at its northern Alberta oilsands project as colder weather and a forecast of rain allows the industry to start sending staff back to work following the devastating Fort McMurray, Alta. wildfires.

Athabasca, which produces bitumen from wells using steam to melt the thick oil, said Tuesday its Hangingstone facility did not suffer any damage from wildfires that crept to within a few kilometres, forcing staff to scramble to safety three weeks ago.

Prior to shutdown, the thermal project commissioned last year had ramped up to 9,000 barrels a day on the way to output capacity of 12,000 bpd. Athabasca said it expects its underground reservoir to recover to normal operating levels over the next several weeks.

Meanwhile, Suncor Energy (TSX:SU) continued to bring workers back to its oilsands mining and thermal projects north of Fort McMurray after emergency officials lifted evacuation orders on the weekend.

A CIBC (TSX:CM) report published Tuesday morning estimated the cash flow impact of lost Suncor production will be about $760 million, while cautioning that number could be reduced by insurance coverage.

"We expect the mining operations will be up to turnaround levels later this week and in situ operations back to mid-turnaround levels next week," CIBC analyst Arthur Grayfer said in a note to investors.

"Assuming there is no additional fire risk, we estimate the downtime from the fire and ramp to turnaround capacity to be three to four weeks, with an additional week to get production back up to full capacity with the completion of the turnaround."

Suncor's mining operations have a capacity of about 250,000 barrels a day but had been reduced by about two-thirds by a maintenance turnaround in its upgrader when the fire broke out. That work will have to be completed before the upgrader output returns to normal.

Suncor's Firebag and Mackay River thermal operations, which were also closed, have combined capacity of about 235,000 bpd.

Syncrude Canada, owned by a consortium that includes Suncor, is also moving to restart operations. It has capacity of 350,000 bpd at its upgrader and Mildred Lake and Aurora mines.

Analysts estimated that more than one million barrels per day of oilsands production were offline at times over the past three weeks as the wildfire forced staff evacuations and the precautionary shutdown of inbound and outbound pipelines. None of the projects has reported substantial damage.

In a Tuesday morning update, provincial emergency officials said the Fort McMurray wildfire had grown to 523,000 hectares, an area almost the size of Prince Edward Island, and was still out of control but moving farther east and northeast away from the city and industrial operations.